Just out of curiosity, I'm running 250lbs on the high side and 20lbs on the low side at 2500rpm on a 1988 300sel a/c system and I do not see any bubbles in the sight glass at all-even when the system starts up. Is that within specs? I misplaced my old a/c manual. Also, the system runs for 50-60 seconds then shuts down and will not cycle back on unless I shut the engine off. Any advise would be highly appreciated. Thanx Nick

I'm at work and don't have the 126 CD-Rom with me, so I can't comment about low/high side pressure.

The system is designed to shut off the A/C compressor if the serpentine belt is too loose. Check out your serpentine belt tension.

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

I tried that after reading your reply - no difference. Perhaps some temp sensor is non-functional. I like to gather all the suggestions in case there's something I can do to remedy the situation, before having to take it in for repairs. All the fuses are ok, and the aux fan works.

Try the SEARCH facility. Much has been said about this problem.

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

Those pressures sound OK. If the sight glass is clear and the system is cooling well, don't touch it!

If you are having system problems with compressor not operating properly, I would build a bypass relay to bypass the speed sensor on the rear of the compressor. It was only there as a precaution and now Mercede has done away with most of them.

You will need a 4 pin relay rated at 30 amps and an Electrical Manual. We sell them on CD if needed.

__________________
Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS